<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no,initial-scale=1.0,maximum-scale=1.0,minimum-scale=1.0"/>
    <title>mobile init one</title>

    <style>
        * {
            margin: 0;
            padding: 0;
        }

        div:nth-child(2) {
            /* 传统盒子模型= width + border + padding */
            width: 200px;
            height: 200px;
            background-color: pink;
            padding: 10px;
            border: 10px solid red;
            box-sizing: content-box;
        }

        div:nth-child(3) {
            /* 有了这句话就让盒子变成CSS3盒子模型 */
            /* padding 和 border 不会再撑大盒子了 */
            box-sizing: border-box;
            width: 200px;
            height: 200px;
            background-color: purple;
            padding: 10px;
            border: 10px solid blue;
        }
    </style>
</head>
<body>
<h2>移动端导航</h2>

<div></div>
<div></div>

</body>
</html>